Dynamic District Heating a Technical Guide for a Flexible CHP Plant Dynamic District Heating – a Technical Guide for a Flexible CHP Plant

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Dynamic District Heating A technical guide for a flexible CHP plant Dynamic District Heating – a technical guide for a flexible CHP plant

In a conventional CHP plant, the operation is based on the network heat load required, with power being sold on the electrical market. A Dynamic District Heating (DDH) plant enables operations on highly volatile electricity markets, thereby providing a path towards a dynamic power market throughout the variations in the required heat load.

By combining the efficiency and secure manner, while adhering to asset owners will achieve higher flexibility of Wärtsilä ICE technology, environmental requirements. economical benefits and greater tailor-made and optimised CHP Energy markets in most parts of value. process, a DDH plant can efficiently the world have to balance distinct Engines utilised for electricity operate on any European electrical needs, but fluctuating demand production produce excess heat. market – more frequently and much combined with variations in the In CHP plants the excess heat from more efficiently than conventional generation of renewables makes engine cooling and exhaust gases CHP plants. balancing very difficult. are harnessed for district heating In future, flexibility will be required Wärtsilä, already today, has the needs. The use of engine technology in order to integrate the growing perfect solution for handling variability featuring flexibility and efficiency, shares of variable renewable energy in thermal power generation. By and a CHP process that is optimised sources in a cost efficient and utilising highly efficient gas engines for performance, results in the plant

2 Network heat load variation (MW) 400 350 300 250 200 150 100 50 0 JanFeb MarApr MayJuneJulyAug SepOct NovDec

Figure 1. Load variation curve of a typical What is a DDH plant? 400 MWth district heating system. The network By combining the efficiency heat load varies dynamically with the ambient temperature. The heat load is high during and flexibility of Wärtsilä the cold seasons of the year and reaches engine technology with a maximum usually in Mid-February. The heat tailored and optimised CHP load is correspondingly low during the warm process, a DDH plant can season. efficiently operate on any electrical market.

being well suited to European energy EPC solution with a lifecycle solutions preparations, speed acceleration, market operations. that guarantee operational reliability and synchronisation to the grid) In a DDH plant, the prime movers and efficiency backed up by expert enables it to operate throughout the are Wärtsilä 34SG gas-fired, spark- advice on optimising power plant year, whenever electricity prices allow ignited, internal combustion engines. operation and maintenance. Wärtsilä profitable running. It also produces The engine is based on state- power plants deliver high simple proportionally more electricity since of-the-art gas technology, which cycle efficiency, even when running it covers a bigger share of the total is under continuous development on part load and in demanding heat demand. to reach higher efficiencies and ambient conditions. A DDH plant is capable of improved performance. In a conventional CHP plant, the adapting to various operational Wärtsilä has a proven track record operation is based on the network modes, thereby ensuring the most in the fast and successful execution heat load required, with power being feasible operational strategy and of large engineering, procurement sold on the electrical market. A electricity production that is highly and construction (EPC) deliveries DDH plant combined with thermal efficient. It also ensures that the heat on a global scale for industrial storage enables operations on volatile demand is met (heat mode). customers, independent power electrical markets, providing a path Because of these dynamic producers and utilities, with power towards a dynamic power market features and different operating plants installed in more than 170 throughout the variations in required modes, the DDH plant can operate in countries. heat load. (Figure 1) any of the various electrical markets, Wärtsilä is one of the largest including day-ahead, intraday, and providers of gas and liquid fired Operation modes secondary control markets. power plants in the world with a A multi-unit Wärtsilä DDH plant with Electricity mode total installed capacity of more than gas-fired engines produces more When the price of electricity allows 70 GW. Currently Wärtsilä operates heat than, for example, a CCGT a positive profit margin, the DDH 34 GW of generating capacity with plant with the same capacity. This is plant can be operated in electrical lifecycle solutions. Wärtsilä power because its wide load range, different power mode. The heat produced will plants are tailored to meet customer operating modes, and short start- either be fed to the DH network or to needs, and the company offers up and ramping time (a Wärtsilä heat storage. If the DH heat demand everything from a basic equipment 34SG power plant requires only is being met by other plants, the delivery to comprehensive turnkey 30 seconds to complete start-up Wärtsilä DDH plant can then reduce

3 its heat production, or even operate water in return. Wärtsilä DDH plants price of electricity. This flexibility can in electrical only mode. ensure that the temperature control be further enhanced with thermal Heat mode is optimised so as to meet local storage of the produced heat. In cases where the heat production DH network temperatures, ambient The size of the DDH plant should from, for example, waste incineration conditions, and other requirements. comply to the annual heat load of the is not sufficient to cover the heat network and the size of the thermal demand, and the thermal storage has Plant configuration storage in order to achieve optimal already been discharged, the residual A Wärtsilä DDH power plant is a utilisation of the plant. With a multi- heat demand can be met by the multi-unit CHP plant that includes unit configuration, the plant size can DDH plant operating in heat mode. engines, boilers and pump modules. be modified for optimisation. In this operating mode, by reducing Existing Wärtsilä DDH plants The DDH power plant includes its electrical power output, the DDH are already in operation in many engines as the prime movers and plant can also be used to balance the countries, including Denmark, main sources for heat. The waste DH network heat demand. Hungary and Italy. Hungarian DDH heat generated by the engines is plants operate in the ancillary recovered in the engines’ cooling Temperature control markets. water circuit and in the exhaust gas The DH water temperature is based DDH plants are capable of high boilers. In addition to hot water for on outside ambient temperatures. efficiency and flexible operation over district heating purposes, waste heat The system’s design is network a broad range of plant loads, and are can also be recovered in the exhaust specific, feeding hot or warm water thus able to respond to the demand gas boiler as steam for heating to consumers and receiving colder for heat, and to fluctuations in the purposes. (Figure 2)

4 District heating network

CHP module

Engine, Wärtsilä 20V34SG

Exhaust gas boiler

Exhaust gas stack

Generator

Electricity

Natural gas

Radiator

Thermal storage

Municipality

Figure 2. The main equipment Figure 3. The practical range for methane numbers in five EU countries. This does not mean in a DDH plant. that customers necessarily experience such a broad range, since locally the gas composition can be close to constant. (Source: The European Association of Internal Combustion Engine Manufacturers, 2014)

The engines a methane number of “0”. Methane, to fully utilise its inherent heat. Different alternatives which has high knock resistance, Generally, raising the lubricating oil Wärtsilä offers many different engines has the number “100.” Other fuels lie temperature enables considerably but the Wärtsilä 34SG model is the elsewhere on this scale. more heat to be recovered from it. most suitable for DDH plants. The SG The fuel gas methane number Additionally, raising the temperature engine is a spark-ignited lean-burn impacts both electrical efficiency and of the lubricating oil will slightly otto cycle gas engine which can be the engine’s output, but the methane boost electrical efficiency. configured with distinct NOX (nitrogen number sensitivity differs according Jacket temperature oxides) ratings, fuel gas methane to the engine tunings. Wärtsilä offers Engine cylinder cooling (jacket numbers, and a range of lube oil the most beneficial engine tuning cooling) is utilised in DDH plants and jacket water temperatures. Each to match the quality of the available to boost the efficiency of the heat selection has an impact on both the fuel gas. Depending on the tuning recovery. Higher efficiency is electrical and heat performance, as of the engine, the de-rating point achieved by increasing the engine well as on the efficiency of the plant. varies between the fuel gas methane jacket temperature in order to numbers of 60 and 80. The indicative Impact of the methane number ensure high heat recovery from the methane number range relative to A fuel’s methane number describes engine jacket’s cooling circuit. five European countries is shown in how well the fuel will burn in the Figure 3. cylinders. Hydrogen, which burns quickly relative to methane, has a Lubricating oil temperature low resistance to knocking, giving it It is important to use the correct temperature of lubricating oil in order

5 HTCAC heat recovery directly tube boiler than in a water tube Flue gas emissions with DH water boiler, thus necessitating more Wärtsilä can deliver the instruments In order to increase heat recovery frequent maintenance stops. and equipment needed for measuring performance and to simplify the In general, the average downtime and monitoring the substance process, the DH water can be for cleaning is longer for smoke tube concentrations and properties of the circulated directly through the boilers than for water tube boilers. flue gas, as required by German law. HTCAC. In conventional systems, Taking into account the higher fouling Wärtsilä DDH plants comply with the DH water and water circulating in rate in a smoke tube boiler, the German authority legislation and use the HTCAC are separated by a heat increased number of maintenance proven technology to fulfil all such exchanger. stops will create additional losses for requirements. plants utilising smoke tube boilers. Wärtsilä offers different NO tuning Boiler and economiser X Water tube boilers are, therefore, engine alternatives. The various NOX Boiler types recommended as they minimise tuning alternatives have different There are two different types of boiler fouling and the time needed for impacts on engine output and available; water tube boilers and cleaning. efficiency. A general rule is that the smoke tube boilers. A smoke tube higher the NO -tuning, the higher the Thermal storage X boiler is one in which hot exhaust electrical efficiency. gas from the engine passes through Due to volatility in electricity prices, The Industrial Emissions Directive tubes running within a sealed power generated during peak hours (IED) requires a NOX maximum container of water. In water tube is typically more profitable than of 36 ppm. With an engine NOX boilers, water circulates in tubes power generated during the night. In tuning above 36 ppm, Wärtsilä heated externally by hot exhaust gas a DDH plant, the generated thermal offers additional fuel gas cleaning from the engine. energy can be stored in thermal equipment in order to meet the IED Water tube boilers are generally storage tanks, also known as heat requirements. Higher NOX tuning more compact than smoke tube storage tanks, in order to decouple of engines means that both CAPEX boilers with the same capacity. The heat production from electricity and OPEX costs are higher, as an boiler packages can be divided into production. emission control system is required high and low temperature sections; With a Wärtsilä DDH power plant in order to comply with the flue gas namely the boiler and economiser, and thermal storage, the variations emission limits. respectively. in power prices and heat demand Depending on the market price can be utilised to maximise the value Boiler pinch points of electricity, a higher NOX tuning The pinch point temperature of the heat and power generation. can still be beneficial since a higher This is achieved by operating the between the exhaust gas and NOX tuning will give greater electrical the water impacts heat recovery engines during these peak hours efficiency from the engine. output and efficiency. Lower pinch and feeding the heat produced into temperatures require more heat the district heating network or to the Noise transfer areas, which adds to the thermal storage tank. With a thermal Noise legislation and guarantees cost of the boiler. However, as heat storage tank tightly integrated into A power plant must meet country- recovery output is increased with the Wärtsilä DDH power plant, the specific legislative noise limitations lower pinch temperatures, the heat benefits can be utilised completely. and requirements. The emission production cost (€/MWhth) is often Such benefits include: limit for all noise sources at a correspondingly lower. Wärtsilä zz The heat output from the engine German industrial site is 70 dB(A). selects the pinch point based on its and thermal storage will substitute Wärtsilä complies with these limits. technology and knowledge of the other investments in heat If the plant is close to a residential markets so as to achieve an optimal generating capacity area, Wärtsilä can guarantee even CAPEX and performance ratio. zz The power plant’s power output lower noise values at the closest will be at maximum load during receptor. Fouling rate and cleaning periods when the power price is With full scope power plant All exhaust gas boilers require high projects Wärtsilä can again ensure occasional cleaning of the heat zz The engine/accumulator will that all the noise limitations for the transfer surfaces in order to decrease the operation of heat plant are fulfilled. For EEQ projects, compensate for fouling. By observing only boilers Wärtsilä guarantees the values over a period of time the increase zz Eventually the value of the (sound power level or surface in the exhaust gas temperature generated power may be boosted averaged sound pressure level) for downstream of the boiler, the need by selling the capacity on the the delivered equipment. for cleaning can be determined. balancing market Fouling is more prevalent in a smoke

6 Wärtsilä technology provides accurate measured and predicted noise levels at distances between 100 and 500 m, to within +3 dB(A) of uncertainty, as specified by ISO 9613. In other words, the results are very reliable. Power plant design from the point of view of noise Wärtsilä’s modularised solutions and advanced engineering skills ensure compliance with the stringent German noise requirements. Among these solutions are: zz Concrete sandwich panels, concrete walls, or double sandwich panel walls for attenuation of engine body noise emissions. zz Individual engine cells zz Extra silencers for the attenuation of noise from the ventilation equipment, intake air inlets and exhaust gas outlets zz Once through cooling (sea or river water) engine cooling is preferred as a means of noise control. zz Ultra low noise radiators with fan specific silencers and sound baffles around the radiators attenuate noise inflicted by radiator fans Figure 4. Typical total plant efficiency as a function of the DH supply and return zz Reactive and dissipative silencers temperature. for the attenuation of exhaust gas noise inside the engine hall and in the exhaust gas stack. Process Wärtsilä has a number of global CHP reference projects. By optimising the process and equipment configuration for each project, Wärtsilä always ensures optimal heat recovery, regardless of the DH temperatures. To reach full flexibility, engine backup cooling of the HT water is needed to enable the plant to be capable of running in electrical only mode. (Figures 4 and 5)

Process systems Figure 5. Indicative plant efficiency as a function of investment cost. Ventilation High efficiencies are achievable, but have an impact on CAPEX. The temperature of the intake air to the engine should be above -20°C. To ensure the function of the engines, the intake air can be heated. Higher

7 Figure 6. In DDH plants, the power house has two floors, with the generating set and auxiliaries on the first floor and the ventilation, exhaust gas heat recovery, and emission reduction equipment on the second floor.

intake air temperatures are also Thermostatic valves Services beneficial from a performance point There are several types of Wärtsilä’s lifecycle solutions for the of view, giving a significant increase thermostatic valve. One major energy industry provide guaranteed in plant efficiency. difference between the valve types operational reliability and efficiency, The temperature of the low is the amount of water leakage, i.e. backed up by expert advice on temperature (LT) water is insufficient how tight and exact the valves are in optimising power plant operation to allow the water to be utilised their control. By selecting the correct and maintenance. Guidance on for heat recovery. However, the LT valves, the thermal performance is equipment performance and water can be used for heating the improved significantly. operations surveillance ensure intake air. As a positive effect of the continued performance and this, the engine turbo acts as a heat Layout maximised uptime of the power pump and transfers heat from the Wärtsilä’s extensive experience from plant. By partnering with Wärtsilä, LT water to the HT water through thousands of power plant projects power plant owners can feel secure, the engine charge air cooler, which provides the basis for the company’s knowing where to get help and can then be utilised for district modularised and optimised plant support when needed. heating. The COP value for this layouts. The power house and Solutions can be customised process reaches about 1.3, which plant layouts are designed to to suit the power plant’s operating means that the HR circuit gains ensure all noise, fire protection, and profile and answer the power plant 1.3 times the LT heat dissipated to maintenance requirements are fulfilled. owner’s and operator’s needs in the the pre-heating of the charge air. In DDH plants, the power house has most efficient way. A further benefit of utilising excess two floors, with the generating set and engine LT water heat is that the heat auxiliaries on the first floor, and the Operations and dissipation required in the radiators ventilation, exhaust gas heat recovery, maintanance is reduced, thus minimising heat and emission reduction equipment on Enter into a partnership where we losses. the second floor. (Figure 6) agree on and work towards shared

8 A DDH in facts and figures Multi-unit power plant sizes from ––4.5 to 500+ MW à investment according to need, with the possibility to increase in stages. 90% total efficiency at any plant ––load High yet flexible power to heat ––ratio, thanks to being able to decouple electricity and heat production Non-spinning (no fuel ––consumption and no emissions) secondary frequency control à Syncronisation within 30 s à Full load in less than 5 min No maintenance impact (EOH) for ––frequent starts and stops More than 20% primary frequency ––control ––Reactive power control

Figure 7. The Györhö cogeneration plant in Hungary with 3 x Wärtsilä 18V34SG engines. productivity goals. The solution Optimised maintenance covers every aspect of the day-to- Make sure that your investment is Abbreviations day operation of your power plant(s) secure and predictable. An Optimised CAPEX Capital Expenditure as well as all related maintenance maintenance agreement transfers the COP Coefficient of and administration tasks. An responsibility for maintenance of your Performance Operation and maintenance power plant to Wartsila. The solution DH District Heating agreement helps to maximise the covers maintenance planning and DDH Dynamic District Heating productive lifetime of your power services whenever needed, with fixed EEQ Engineering, plant and your return on investment, prices for inspection, remote operational Equipment Delivery and the solution is tailored to support, spare parts, training and EPC Engineering, Procurement, your specific needs – including maintenance. Construction performance and lifecycle cost GW Gigawatt guarantees Project execution HR Heat Recovery Wärtsilä has a proven track of around HT High Temperature Guaranteed asset HTCAC High Temperature performance 1000 EPC and EEQ projects in more than 100 countries globally. Charge Air Cooler Ensure the reliability and availability Wärtsilä meets customer needs and IED Industrial Emissions Directive of your power plant. With our requirements by customising every IPP Independent Power Producer solution, you can manage operations project. Wärtsilä is capable of handling LO Lubricating Oil and outsource the maintenance and everything from fast track EEQ projects LT Low Temperature its management to us. An onsite to full scope EPC projects. OPEX Operational Expenditure support engineer, online data and With experienced and certified remote operational support enable project execution personnel, Wärtsilä advanced support and immediate understands the requirements for power response from our experts to ensure plant execution projects and is fully able reliable operation of your power to handle and manage the complete plant. range of contracting arrangements.

9 References

Mainz, Germany KRAFTWERKE MAINZ-WIESBADEN Fuel Gas Prime mover 10 x Wärtsilä 20V34SG Electrical power 100 MWe Heating power Up to 96 MWth Delivery 2019

Cheong Soo, Korea CHEONG SOO Fuel Gas Prime movers 3 x Wärtsilä 20V34SG Electrical power 25.4 MWe Heating power 21.3 MWth Delivery 2010 & 2015

Bolgiano, Italy BOLGIANO Fuel Gas Prime mover 2 x Wärtsilä 20V34SG Electrical power 19.4 MWe Heating power 9 MWth Delivery 2014

10 Sasolburg, South Africa SASOLBURG Fuel Gas Prime movers 18 x Wärtsilä 20V34SG Electrical power 175 MWe Steam delivery 41.6 MWth Delivery 2012

Ujpalota, Hungary UJPALOTA Fuel Gas Prime movers 3 x Wärtsilä 20V34SG Electrical power 29 MWe Heating power 19 MWth Delivery 2004

Ringkøbing, Denmark RINGKØBING Fuel Gas Prime movers 1 x Wärtsilä 20V34SG Electrical power 8 MWe Heating power 9.6 MWth Delivery 2002

11 Wärtsilä Energy Business is leading the transition towards a 100% renewable energy future. As an energy system integrator, we understand, design, build and serve optimal power systems for future generations. Wärtsilä’s solutions provide the needed flexibility to integrate renewables and secure power system reliability. Our offering comprises engine- based flexible power plants – including liquid gas systems – hybrid solar power plants, energy management systems and storage and integration solutions. We support our customers over the lifecycle of their installations with services that enable increased efficiency and guaranteed performance. Wärtsilä has 70 GW of installed power plant capacity in 177 countries around the world.

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